Microcapsules having activated release of core material therein - Patents

Microcapsules having activated release of core material therein
Agent: Senniger Powers Leavitt And Roedel - St Louis, MO, US
Inventors: Michael E. Seitz, Ronald J. Brinker
Class: 504359000 (USPTO), A01N025/28 (Intl Class)
#20050277549
12/15/05

The present invention is directed to microcapsules having polymeric shells that possess blocking groups (e.g., amine-blocking groups), the removal or cleavage of which act to initiate release of the core material therein, or increase the rate at which such core material is released. The present invention is further directed to the formulation of said microcapsules in aqueous dispersions, to the preparation of said microcapsules, and to the use of such microcapsules and dispersions thereof.
SUMMARY OF THE INVENTION
[0007] Briefly, therefore, the present invention is directed to a microcapsule comprising (i) a substantially water-immiscible core material comprising a biologically active compound, and (ii) a shell wall which encapsulates the core material, wherein the shell wall is formed by an interfacial polymerization of an isocyanate monomer with an amine monomer in an encapsulation shell-forming polymerization, and further wherein said shell wall polymer backbone comprises a nitrogen-containing repeat unit therein and at least one blocking group thereon, the breaking of a bond to said blocking group being effective to increase a rate at which the microcapsule releases the biologically active compound.
[0008] The present invention is further directed to a method of increasing a rate of release of an encapsulated biologically active compound from a microcapsule comprising a shell wall formed by an interfacial polymerization of an isocyanate monomer with an amine monomer in an encapsulation shell-forming polymerization, said shell wall polymer backbone comprising a nitrogen-containing repeat unit therein having at least one blocking group thereon. The method comprises contacting said microcapsule with a cleaving agent, the cleaving agent being selected to cleave a bond to the blocking group.
[0009] The present invention is further directed to a method for the preparation of an aqueous dispersion of microcapsules. The method comprises (i) creating an oil-in-water emulsion comprising an aqueous external phase and a substantially water-immiscible internal phase, the external phase comprising water, an emulsifying agent, and a first amine monomer comprising an amine blocking group, said internal phase comprising an isocyanate monomer and a biologically active compound; and, (ii) reacting the first amine monomer and the isocyanate monomer via interfacial polymerization to encapsulate a substantially water-immiscible core comprising the biologically active compound within a shell comprising a polymer which is a reaction product of the first amine monomer and the isocyanate monomer, wherein the polymer comprises a backbone and a blocking group bonded to an amine in the backbone and wherein the blocking group is subject to removal, removal of the blocking group being effective to increase a rate of release of the biologically active compound from the microcapsules.
[0010] The present invention is still further directed to a method for the preparation of an aqueous dispersion of microcapsules. The method comprises (i) creating an oil-in-water emulsion comprising an aqueous external phase and a substantially water-immiscible internal phase, the external phase comprising water, an emulsifying agent, a first amine monomer and a blocking agent effective for blocking the amine functional group of said first amine monomer, the internal phase comprising an isocyanate monomer and a biologically active compound; (ii) reacting said first amine monomer and said blocking agent to form a blocked amine functional group; and, (iii) reacting the first amine monomer and the isocyanate monomer via interfacial polymerization to encapsulate a substantially water-immiscible core comprising the biologically active compound within a shell comprising a polymer which is a reaction product of the amine monomer and the isocyanate monomer, wherein the polymer comprises a backbone and a blocking group bonded to an amine therein, and wherein breaking of a bond to the blocking group is effective to increase a rate of release of the biologically active compound from the microcapsules.
[0011] The present invention is still further directed to a method for the preparation of an aqueous dispersion of microcapsules. The method comprises (i) creating an oil-in-water emulsion comprising an aqueous external phase and a substantially water-immiscible internal phase, the external phase comprising water, an emulsifying agent, a first amine monomer, the internal phase comprising an isocyanate monomer and a biologically active compound; (ii) reacting the first amine monomer and the isocyanate monomer via interfacial polymerization to encapsulate a substantially water-immiscible core comprising the biologically active compound within a shell comprising a polymer which is a reaction product of the amine monomer and the isocyanate monomer; and, (iii) reacting said polymer with a blocking agent effective for blocking amine functional groups in said polymer to form a polymer comprising a backbone and a blocking group bound thereto, wherein breaking of a bond to the blocking group is effective to increase a rate of release of the biologically active compound from the microcapsules.
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